Copolymers of maleic anhydride and a compound having an unsaturated group have found their application in various fields. For example, a salt of a diisobutylene-maleic anhydride copolymer is used as a dispersant in an aqueous system as described in Cement & Concrete, No. 478, p. 7 (1986), and an ethyl or butyl ester of a methyl vinyl ether-maleic anhydride copolymer is used in cosmetics as described in Nippon Hanyo Keshokin Genryoshu, p. 161, K. K. Yakuji Nipposha (1985). It has been proposed to use a copolymer of a polyoxyalkylene monoalkenyl ether and a maleic ester of a polyalkylene glycol or a monoalkyl ether thereof as a dispersant for cement as disclosed in JP-A-59-162162 (the term "JP-A3[ as used herein means an "unexamined published Japanese patent application").
However, copolymers of an olefin, e.g., diisobutylene, and maleic anhydride, while non-neutralized, are soluble only in limited kinds of solvents such as toluene. When converted to their salts, they are soluble only in water. Further, having an average molecular weight in the thousands, these copolymers are limited in application.
Esters of methyl vinyl ether-maleic anhydride copolymers are poor in lipophilic properties and therefore unsuitable for use as an emulsifier or dispersant.
Copolymers of a polyoxyalkylene monoalkenyl ether and a maleic ester of a polyalkylene glycol or a monoalkyl ether thereof, though effective as additive for cement, exhibit poor lipophilic properties. Further, similarly to the .alpha.-olefinmaleic anhydride copolymers, they are of limited application due to their average molecular weight in the thousands.